Iv PRACTICAL DIRECTIONS 317 



large ectoderm cells. These extend longitudinally, and lie against the 

 oviter surface of the^supporting lamella. Sketch. 



Examine transverse sections through the body or tentacles, prepared 

 as directed on p. 136, after killing and fixing the] specimens as 

 above. Work through 6—8 again, noting the various cells and their 

 nuclei, &c. Observe especially — 



13. (o) The contractile processes of the ectoderm cells, which will be cut 

 across transversely, so as to appear as dots just outside the supporting 

 lamella ; (b) the amceboid and vacuolated character of the endoderm cells. 

 (Special methods of preparation are necessary in order to shovif the 

 flagella. ) Sketch. 



Bougainvillea.' 



If possible, examine first alive, and then kill and stain as directed in 

 the case of Hydra. Examine under the microscope and note ; — 



a. Colonial stage, r. The^j/n/raKM.?, attached to a common branching 

 stem : compare their structure vjfith that of Hydra. 2. The medusa-- 

 buds. 3. The cuticular exoskcleton supporting the colony. 



b. Medusa stage. I. The umbrella, tentacles, velum, iiianubriiliii, 

 mouth, radial and circular canals, ocelli, and gonads, 



^ Specimens living or preserved, both of the colonial and medusEt 

 stage of Bougainvillea or some allied form (e.g. Obelia), can be obtained 

 from any Marine Biological Laboratory ; or the fresh-water Cordylophorcl, 

 will answer the purpose as far as the colony is concerned, but it has no 

 medusa stage. 



